The patented hybrid-nuclear energy production process emerged from several observations, including: (1) compressed air is a key to modern energy production; (2) about half the power produced by a gas turbine is used to compress air; (3) nuclear fuel is inexpensive. The unique and never previously proposed hybrid combines the strengths of the underlying technologies to yield a transformational quantum leap in the production of energy. (Figure1)
The hybrid is physically much smaller and significantly safer than today’s nuclear plants, although the hybrid’s power output is comparable to a large conventional nuclear plant.
The hybrid’s nuclear fuel cannot melt nor can the reactor cause explosions and fires. The public is always safe, even if water, electrical power and plant operators are unavailable.
Reactor decay heat can always be passively removed by air naturally circulating within the containment building whose steel shell is cooled by ambient air. Additionally, a number of active systems (requires electrical power and water) are also available.
The containment building prevents release of radioactive material to the environment, even if the reactor vessel fails. This is quite unlike the design philosophy used with water reactors as well as conventional gas reactors.
Reactor and nuclear systems located underground (Figure 2)
-- Defense in-depth protection
-- Safe from tornados, hurricanes and plane crashes
Reactor and nuclear systems located underground.
-- Exceptionally secure.
Security needs minimized.
-- Safe from earthquakes
Reactor building sits on seismic isolators
-- Reactor cannot melt, always cooled.
Several passive systems remove nuclear decay heat
-- Radioactive material cannot escape into the environment.
The hybrid can be configured to provide power and steam when the reactor and combustion turbine not operating. Forced draft fans and burners inside the Heat Recovery Steam Generator allow the plant to operate as a conventional gas boiler. No nuclear plant of any type or size can match this capability. (Figure 3)
High pressure on inside, low-pressure on outside. Pressurized helium coolant is circulated through the reactor, heated up and sent to a turbine with lower pressure cooler helium directed back to the outside of the reactor, then to a heat exchanger, cooled and then directed to a compressor where the helium is re-pressurized and sent back to the heat exchanger, partially heated and once again sent to the reactor. This configuration dramatically reduces manufacturing costs by allowing the use of welded plate instead of large heavy-walled forgings, as envisioned by conventional gas reactor designs.
The hybrid’s outer vessels and pipes are designed and built to the highest standards – the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Rules for Construction of Nuclear Facilities; Division 5, High Temperature Reactors. The vessels and outer piping are constructed of the same material routinely used for pressurized water reactors – technically SA508/533 steel. However, plates are used instead of the heavy forgings used with conventional reactors. Unlike conventional reactors, failure of the hybrid’s reactor vessel does not lead to massive off site radiation releases, thus the hybrid’s use of more cost effective plate.
The hybrid’s inner vessels and pipes are designed and built to the very high standards – the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section VIII Power Boilers. The very stringent requirements (ASME Section III) used for the outer pressure boundary components are not necessary for the inner vessels and piping owing to the extensive defense-in-depth design of the hybrid.
Hybrid Combustion Turbine
The hybrid employs a standard large gas turbine modified to use a smaller compressor with the bulk of the air flowing laterally into the machine. The design is somewhat similar to the methods used by machines burning gasified coal. (Figure 6)
The turbo-compressor is based on proven heavy-frame and aero-derivative combustion turbines used in the power industry. The variable speed turbo-compressor rotates at about ~3000 R.P.M. and avoids material stress issues associated with much faster rotating designs. This feature also allows the hybrid to effectively optimize air flow to the combustion turbine, thereby allowing the hybrid to produce about 15% more power than a conventional fixed-speed (3600 R.P.M.) configuration operating at standard conditions (59 F).
Proven hydrodynamic oil bearings are used on the outboard ends of the shaft/rotor assembly with in-board magnetic bearings used within the helium environment. Multiple shaft seals are used to minimize helium leakage. However, minimal leakage is expected because the differential pressure across the shaft seals is very small due to the interface with the main air compressor which operates at similar pressures.
The operating temperature of the helium turbine is relatively low (~1540oF) by combustion turbine standards where high-firing temperatures (+2500oF) are common. As such, overhaul of the turbo-compressor will be infrequent. The turbo-compressor is designed to be removed as a unit similar to the methods used with power industry aero-derivative combustion turbines. This approach accelerates overhauls and minimizes radiation exposure by maintenance crews.
The hybrid employs elements of the control methods routinely used by combustion turbines. Both the helium and air compressors employ variable pitch inlet stator vanes to control the flow of gas through the machines. (Figure 7)
- Short-term (seconds/minutes) – Rotate variable stator vanes at inlets of the compressors.
- Mid-term (hours) – Alter turbo-compressor speed by reducing reactor power using maneuvering rods.
- Long-term (multiple hours) – Add/remove primary system helium.
Primary Heat Exchanger
The primary heat exchanger consists chiefly of a recuperator and pre-cooler made up of compact heat exchanger “cartridges” constructed from explosively welded plates. Full-flow sintered metal filters are used to reduce particulates (and radioactive particles) in the helium to minimize fouling of the turbo-machinery as well as minimize system radioactive contamination, thereby aiding maintenance efforts. The filters are replaced using the fueling machine.
A two-train helium purification system is used to further reduce coolant chemical impurities such as hydrogen, carbon monoxide, water vapor, carbon dioxide, methane, oxygen, etc. The purification system consists of pre-charcoal traps, fixed bed filters, coolers, molecular sieve traps, cold charcoal traps, and gas circulators.
Economics and Environmental
The hybrid's economics are exceptionally competitive while the environmental impacts are exceptionally benign.